MUSES-C was the code-name used for Hayabusa during development. MUSES stands for Mu Space Engineering Spacecraft (because the satellite was launched from a Mu rocket) and indicates a particular series of experimental engineering satellites. MUSES-C-Hayabusa-is the third in the MUSES series, which includes MUSES-A, the Hiten probe, and MUSES-B, the Haruka VLBI observation satellite.

An electric propulsion engine that ionizes xenon gas and uses an electrical acceleration system is called an ion engine. Due to its high efficiency, this technology is also expected to be important for future investigation of moons and planets. Hayabusa incorporates four newly developed ion engines that use microwaves.

Asteroid Probe Hayabusa's Return to Earth (PDF file, 6.3 MB)"3-1 Advanced ion engine" (page 5) (opens a PDF file on JAXA website)

Itokawa is a solar system asteroid that belongs to the Apollo group of near-Earth asteroids (celestial bodies that have orbits near Earth). Itokawa was discovered on September 26th, 1998, by an American team of aerospace researchers belonging to the LINEAR (Lincoln Near-Earth Asteroid Research) project.
After the asteroid was selected as Hayabusa's investigative target, the ISAS requested that the LINEAR team name the asteroid after Hideo Itokawa, a pioneer of Japanese rocket development, and the name was approved by the International Astronomical Union on August 6th, 2003, and announced as the official name.
Exploring the Asteroid Itokawa:Subsequent Analysis and Research
(links to ISAS website)

A chemical propulsion thruster is a device used to eject gas from a small rocket engine and use the resulting reaction force for attitude control and fine position control of the satellite. Hayabusa uses 12 chemical propulsion thrusters arranged into two systems.

The re-entry capsule is a small collection capsule that has a diameter of 40 cm and was used to carry the sample from Itokawa. After the capsule separates from Hayabusa, it will directly re-enter Earth's atmosphere from interplanetary orbit at a velocity of more than 12 km/s. The maximum amount of aerodynamic heat the capsule will be dozens of times stronger than the Space Shuttle and several times more intense than the heat Apollo was subject to upon returning from the moon. The surface temperature will reach several thousand degrees Celsius. One of the greatest challenges for the Hayabusa design team was to develop heat shielding materials that could withstand these kinds of temperatures.

Asteroid Probe Hayabusa's Return to Earth (PDF file, 6.3 MB)"2-2 Recovery of "HAYABUSA" re-entry capsule" (page 4) (opens a PDF file on JAXA website)

Swing-by refers to a technique for using the gravity of a celestial body to change the direction or speed of a satellite. The orbital motion of celestial bodies can be used to increase or reduce the speed of a satellite. Hayabusa is the first spacecraft ever to demonstrate the ability to use both the usual Earth swing-by and ion engine propulsion.

The solar array paddle is an important part that generates the power essential for operating the equipment on the probe. During the launch, the paddle is attached to the satellite in a folded state, then the metal fittings are severed following the initial orbit injection to unfold the paddle. The attitude of the paddle is generally controlled so that the surface to which the solar array is fixed faces the sun. The Hayabusa solar paddle is approximately 5.7 m from tip to tip, and it generates approximately 2.6 kW of power at a distance of 1.0 AU*.
* AU is the abbreviation for Astronomical Unit, a measure of distance. 1.0 AU indicates the average distance between Earth and the sun.

The target marker is a device that served as a beacon guiding the way to the asteroid surface. Hayabusa dropped the target marker as the probe got close to the asteroid Itokawa. The target marker had a diameter of approximately 10 cm, and the reflective sheet attached to the marker glittered brightly, reflecting the light flashed by Hayabusa. Based on images of the marker taken by its camera, Hayabusa detected the horizontal speed and canceled the same speed to touch down on Itokawa.On November 20th, 2005, Hayabusa dropped the target marker, which was signed by 880,000 people from 149 countries.
Hayabusa's Return Journey to Earth: With the Hopes of 880,000 People (links to JAXA website)

Touchdown refers to the landing of Hayabusa on Itokawa, which has a weak gravitational pull, for a very short time (approximately one second) to obtain a sample.
To obtain this sample, the instant a piece of Hayabusa equipment called a sampling horn touched the surface of Itokawa, Hayabusa was supposed to shoot a metal pellet that weighs several grams into Itokawa's surface and collect the particles that flew up as a result. This was an extremely inventive concept.

The term "beacon" commonly refers to a radio transmitter, but in reference to satellites, this term is sometimes used to refer to a radio wave not carrying much information that is emitted from a satellite to Earth to simply indicate its existence (by the fact that it emits a radio wave).

Specific impulse is an indicator of the performance of a rocket engine. It indicates the fuel efficiency of a rocket engine and is defined as the number of seconds for which a rocket engine can produce 1 N of power from one 1 kg of propellant. The larger this value is, the less propellant is needed to achieve acceleration to a high velocity.

The Hiten engineering satellite was launched in 1990 and used to gain orbit control skills such as the swing-by information required for investigating moons and planets.

The newton (N) is a unit of force. One newton is defined as the amount of force necessary to accelerate a mass of 1 kg at a rate of 1 m/s² and is equal to force of gravity exerted on a mass of 98 grams (equivalent to a small apple). One micronewton (µN) is one 1 millionth of one newton.

This equipment is used to stabilize the attitude or change the direction of a satellite without using rocket or jet propulsion. The satellite attitude is controlled using a flywheel. When the fly wheel is rotated one way, the spacecraft turns the other way (due to the conservation of angular momentum). Hayabusa was equipped with three reaction wheels.

The laser altimeter emitted laser pulses to measure the distance between the probe and the asteroid. In addition to being an extremely important navigation sensor for Hayabusa to touch down on Itokawa, the laser altimeter carried out scientific observation such as measuring the shape of the asteroid surface and its gravity based on the force of rotation. Hayabusa's laser altimeter was capable of measuring distances in the extremely wide range of 50 m to 50 km, making it usable both for approaching and touching down on the asteroid.